The present invention relates to a particle-size distribution measuring apparatus, and particularly to an apparatus in which the pH value is measured and the state of the particle dispersion can be monitored from the pH value and which allows calculating an ideal pH value for obtaining an ideal particle-size distribution state therefrom.
In the prior art for managing the product quality in each of the production steps in a factory, a batch test using a particle-size measuring apparatus is conventionally employed. In such a batch test, a particle-size measuring apparatus extracts a batch sample (i.e. specimen to be measured) and measures the particle-size distribution thereof. Namely an operator in the factory extracts some quantity of a sample to be measured (hereinafter referred to as xe2x80x9csamplexe2x80x9d) by particle-size distribution measuring apparatus from the piping in the factory. Then, he or she introduces the sample into the particle-size distribution measuring apparatus and executes the measurement. Corresponding to the result of the measurement, it is decided whether a correct and proper working material is supplied to each of the production steps in the factory.
For example, there is a case in which an abrasive material for grinding wafers is supplied as a working material through piping in a factory. If this abrasive material aggregates, the aggregated abrasive material may create flaws on the surface of wafers. Thus, it is conventional to measure the particle-size distribution of the abrasive material to avoid such unfavorable incidents which may occur during such a fabrication process.
When particles are in a dispersion state, the surrounding medium and ionicity have a greater effect on smaller particles, which leads to an aggregation of the particles. Thus, also in the prior art, the pH value of the extracted sample is measured in order to estimate the influence of charges and ionicity. Also, the degree of the dispersion is estimated according to the measured particle-size distribution in the same state.
However, the aforementioned measurements of the pH value and the particle-size distribution are carried out using separate apparatuses, and the data of those measurements are outputted separately. Thus, it is difficult to find the correlation between the pH value and the particle-size distribution. Another problem is that the particle-size distribution and the degree of dispersion of the corresponding sample can not be measured simultaneously.
The present invention takes into consideration the aforementioned problems in the prior art. An object of the present invention is to propose a particle-size distribution measuring apparatus which allows measuring simultaneously the dispersion state of particles in the suspension medium and the particle-size distribution.
In order to resolve the aforementioned problems, the particle-size distribution measuring apparatus according to the present invention measures particle-size distribution of particles included in a sample, and further comprises a pH meter for measuring the pH value of the sample and an information processing portion. The information processing portion determines the relation between the pH value and the particle-size distribution on the basis that the pH value measured by the pH meter and the measured particle-size distribution are in the same state.
The information processing portion determines the relation between the dispersion state of the sample and the particle-size distribution based on the measured value of the pH meter and the measured particle-size distribution. Therefore, the properties of the sample can be more accurately determined. As a result, it is possible to calculate a pH value which permits maintaining a state having a desired particle-size distribution.
It is possible to change the dispersion state of a sample by monitoring and adjusting the pH value of a sample which is introduced into the particle-size distribution measuring apparatus. Or, inversely, it becomes possible to obtain a desired dispersion state and a particle-size distribution of the particles by monitoring the particle-size distribution and by changing the pH value.
In both cases, the change of the pH value and the particle-size distribution can be simultaneously and properly measured in a same state. Therefore, the reliability of the measured value can be improved.
In a case that the particle-size distribution measuring apparatus further comprises a preparation portion for previously adjusting the pH value of the sample by adjusting the pH value of a sample by the preparation portion in a sequential manner, from the change of the particle-size distribution corresponding to each of the pH values, the relation between them is automatically obtained in a sequential manner.
In a case that the information processing portion is connected with a host information processing system in the factory so that they can communicate mutually, and by which the information processing portion outputs the result of the measurement of the particle-size distribution to the host information processing system, the system can manage the fabrication processes in the factory. The host information processing system can manage each fabrication process more accurately, using the relation between the dispersion state and the particle-size distribution of the sample measured by the particle-size distribution measuring apparatus. For example, when particles dispersed in a dispersion medium as working material is supplied via piping in a factory, an ideal pH value for making an ideal particle-size distribution of the particles is obtained. The pH value can be adjusted according to the ideal pH value. Therefore, a high preciseness working can be assured, correspondingly.